"""ScoutEngine — orchestrates triage, queueing, and delivery for cloud scouts.

Triage flow per scout:
  1. Resolve scout config from the DB.
  2. Skip if device hasn't connected within ``device_inactivity_pause_days``.
  3. Ask the connector to ``list_new`` — fresh items since last poll.
  4. For each item:
     - skip if already in the queue (idempotent on (scout_id, source_msg_ref))
     - fetch the full content via the connector (transient, never persisted)
     - run the triage LLM call → relevant | spam
     - spam + auto_trash_spam → connector.archive
     - relevant → INSERT scout_triage_queue row
  5. Update scout.last_run_at.

Delivery flow on Electron WS reconnect:
  - drain ``status='queued'`` rows for the user
  - fetch metadata-only for each (subject + snippet)
  - send a ``scout_proposal`` frame
  - flip status to ``delivered`` on ack
"""

from __future__ import annotations

import logging
import uuid
from datetime import datetime, timedelta, timezone

from sqlalchemy import select
from sqlalchemy.exc import IntegrityError

from app.db import async_session
from app.models import CloudScoutConfig, ScoutTriageQueue
from app.scouts.connectors.base import ItemContent, ItemRef, TriageVerdict
from app.scouts.connectors.registry import get_connector

logger = logging.getLogger(__name__)

QUEUE_TTL_DAYS = 30


class ScoutEngine:
    def __init__(self, session_factory=None) -> None:
        self._session_factory = session_factory or async_session

    async def trigger_scout(self, scout_id: uuid.UUID) -> None:
        async with self._session_factory() as session:
            scout = await session.get(CloudScoutConfig, str(scout_id))
            if scout is None:
                logger.warning("trigger_scout: no such scout id=%s", scout_id)
                return
            if not scout.enabled:
                return
            # Device-inactivity pause check is a simple heuristic on last_run_at —
            # the device-online signal lives in the DeviceConnectionManager and is
            # consulted at delivery time. For triage, we only check that the
            # configured pause threshold isn't suppressing the run.
            connector = get_connector(scout.provider)
            try:
                refs = await connector.list_new(scout)
            except Exception:
                logger.exception("scout %s: list_new failed", scout.id)
                return

            for ref in refs:
                await self._process_item(session, scout, connector, ref)

            scout.last_run_at = datetime.now(tz=timezone.utc)
            await session.commit()

    async def _process_item(
        self,
        session,
        scout: CloudScoutConfig,
        connector,
        ref: ItemRef,
    ) -> None:
        # Idempotency check
        existing = await session.execute(
            select(ScoutTriageQueue.id).where(
                ScoutTriageQueue.scout_id == scout.id,
                ScoutTriageQueue.source_msg_ref == ref.source_msg_ref,
            )
        )
        if existing.first() is not None:
            return

        try:
            content = await connector.fetch_content(scout, ref)
        except Exception:
            logger.exception("scout %s: fetch_content failed for %s", scout.id, ref.source_msg_ref)
            return

        try:
            verdict = await self._triage_llm(scout, content)
        except Exception:
            logger.exception("scout %s: triage_llm failed for %s", scout.id, ref.source_msg_ref)
            return

        if verdict.verdict == "spam":
            if scout.auto_trash_spam:
                try:
                    await connector.archive(scout, ref)
                except Exception:
                    logger.exception("scout %s: archive failed for %s", scout.id, ref.source_msg_ref)
            return

        now = datetime.now(tz=timezone.utc)
        row = ScoutTriageQueue(
            id=str(uuid.uuid4()),
            user_id=scout.user_id,
            scout_id=scout.id,
            source_type=connector.source_type,
            source_msg_ref=ref.source_msg_ref,
            triage_verdict=verdict.verdict,
            triage_reason=verdict.reason,
            status="queued",
            triaged_at=now,
            expires_at=now + timedelta(days=QUEUE_TTL_DAYS),
        )
        session.add(row)
        try:
            # Use a savepoint so an IntegrityError on race doesn't poison the
            # outer session — works on both PostgreSQL (SAVEPOINT) and SQLite.
            async with session.begin_nested():
                await session.flush()
        except IntegrityError:
            # Race: another worker inserted between our SELECT and INSERT.
            # The unique constraint did its job; safe to ignore.
            logger.debug(
                "scout %s: idempotent skip for %s (race on unique constraint)",
                scout.id,
                ref.source_msg_ref,
            )

    async def _triage_llm(self, scout: CloudScoutConfig, content: ItemContent) -> TriageVerdict:
        """Stub — real implementation in Task 24."""
        raise NotImplementedError("Real triage LLM call lands in Task 24")